You may find yourself in a situation where the Linux kernel crashes or hangs without
any output on the console. The first attempt to get more information in such a situation
is a Post Mortem dump of the log buffer - often the Linux kernel has already collected
useful information in its console I/O buffer which just does not get printed because the
kernel does not run until successful initialization of the console port.

Proceed as follows:

Find out the virtual address of the log buffer;
For 2.4 Linux kernels search for "log_buf":
2.4 Linux:

bash$ grep log_buf System.map
c0182f54 b log_buf

Here the virtual address of the buffer is 0xC0182F54
For 2.6 kernels "__log_buf" must be used:

bash$ grep __log_buf System.map
c02124c4 b __log_buf

Here the virtual address of the buffer is 0xC02124C4

Convert to physical address: on Power Architecture® systems, the kernel is usually configured for
a virtual address of kernel base (CONFIG_KERNEL_START) of 0xC0000000.
Just subtract this value from the address you found. In our case we get: